Felt dizzy and like I was going to pass out while on Cozumel dive, what could it be?

[ERRN]

This is not medical advice because I am not certified to, nor know enough to give it. We frequently see patients in the ED with similiar symptoms who are in there 20-30's. After a negative cardiac workup and instructions for possibly a holter monitor placement outpatient they are often diagnosed with having had a vasovagal episode, plenty of sites like Mayo clinic can list some of the triggers and suggested ways to manage or avoid.